May 2026 QQ: “Proconvertin” Response

Our May 2026 Quick Question was a quiz and a “walk down memory lane.” Our 28 responders to the lead, “What factor was once named Proconvertin or SPCA?” responded as follows:

1. IV: 2 (7%)
2. V: 4 (14%)
3. VI: 1 (4%)
4. VII: 18 (64%)
5. IX: 3 (11%)

We’ve largely abandoned our proper noun terminology except for fibrinogen (I), prothrombin (II), and thrombin (IIa). I’ve attached a table from Corriveau DM: Plasma Proteins: Factors of the Hemostasis Mechanism in Corriveau DM, Fritsma GA. Hemostasis and Thrombosis in the Clinical Laboratory, Lipincott, 1988, which lists all the names in use before we moved to using the Roman numeral nomenclature. You’ll see that IV was assigned to Calcium and VI was not assigned. I’m assuming that our respondents included several “seasoned clotters.”